(1) Field of the Invention
The present invention relates to anti-lacerative window glass units which have excellent impact resistance and prevent skins, etc. of human heads from being damaged with broken pieces of a glass body of a sandwich structure when an automobile collides with an object. More specifically, the present invention relates to anti-lacerative window glass units which have excellent impact resistance and in which intermediate films of a multilayer structure (hereinafter referred to as "multilayer structure intermediate films") composed of at least two kinds of different polymers are interposed between two exterior plate-like members which are composed of different kinds of organic polymers or the same kind of the organic polymer or between two exterior plate-like members which are composed of an organic polymer and an inorganic material, respectively When in use, it is necessary to arrange the exterior plate-like member of the organic polymer material on a person's side ("Person's side" is used throughout the specification and claims to mean an interior side of a window in a house, an automobile, etc.). The invention also relates to a method of fitting such anti-lacerative window glass laminates to window frames, automobile bodies, etc.
(2) Related Art Statement
Materials conventionally used as wind shield in automobiles have been improved in the chronological order from a tempered glass, a partially tempered glass, a laminated safety glass to a anti-lacerative laminated glass aiming at enhancing the safety. To the contrary, the number of glasses necessary increases to two from one and an organic resin film is bonded to the glass on a vehicle interior side. Thus, disadvantageous factors occur from the economical standpoint, for instance weight increase and cost-up.
That is, anti-lacerative window glasses which have conventionally been used as safety glass such as windshield glass units each comprise a laminated glass unit using two glass plates as a fundamental structure, and possess an exterior sheet composed of an organic polymer bonded to a person's side of a fundamental structure. Since the laminated glass plates as the fundamental structure themselves essentially have impact resistance, such anti-lacerative window glass units may be called high safety windshield glass. However, a problem remains unsolved that economically disadvantageous factors such as weight increase, cost-up, etc. should surely be solved.
That is, if the number of a glass plate in the glass laminate as the fundamental structure of the conventional anti-lacerative window glass unit is decreased to one to reduce the weight and cost of the windshield glass, economically unmeasurable effects will be obtained.
However, since glass itself is a brittle material, a sufficient penetrating resistance cannot be exhibited only by a countermeasure such as a lining of an urethane base film, polyvinylbutyral/hard coat polyester film or ethylene-vinylacetate copolymer/hard coat polyester film. Thus, it is a present situation that safety glasses which can well withstand practical uses have not been obtained.